Abstract B064: The Aurora kinase A-inhibitor, alisertib, is a potential candidate for combination with immunotherapy in small cell lung cancer

Abstract

Abstract Background: Small cell lung cancer (SCLC) is characterized by a loss of TP53 and RB1 and by amplification of MYC in about 25% of patients. Our group and others have shown that MYC-driven SCLC cell lines are vulnerable to Aurora Kinase A (AURKA) inhibition. Alisertib, a selective AURKA inhibitor, has also shown clinical efficacy in MYC-positive relapsed SCLC patients in combination with paclitaxel in a phase II trial (NCT02038647). AURKA regulates DNA chromosome alignment during cell division and thus its inhibition results in mitotic stress and subsequently DNA damage. We have previously demonstrated that DNA damage response (DDR) inhibitors synergize with immune checkpoint inhibition in SCLC in vivo models by activating a STING-mediated innate immune response. Based on these findings, we hypothesized that AURKA inhibition may activate the STING pathway and induce PD-L1 expression in SCLC. Methods: We compared AURKA gene expression among a panel of SCLC and NSCLC cell lines and, similarly, in tumor versus normal tissue in SCLC clinical dataset (Sato et al.). In parallel, we explored the landscape of STING and immune genes expression in two SCLC clinical datasets (George et al. and Sato et al.).We tested human and GEMM-derived SCLC cell lines for changes in immune and DDR-related protein expression by Western blot analysis after treatment with the AURKA-i alisertib. Results: AURKA gene expression was higher in SCLC cell lines as compared to NSCLC cell lines (p=0.023) and in SCLC tumors compared to normal tissue (FC=1.6; p<0.001), thus making AURKA an attractive target in SCLC. Furthermore, in SCLC clinical datasets, we found that CXCL10 and CCL5, the two downstream chemokines of STING pathway, are highly expressed in about 30% SCLC tumors and their expression is significantly associated with CMYC (Spearman Rho>0.45, p<0.001), possibly due to high baseline levels of replication stress and also to CD274, CD8 and other markers and chemokines suggestive of an inflamed immune microenvironment. We observed that in vitro treatment with alisertib (1µM for 72 hours) further increases the level of phospho-H2AX protein, a marker of DNA damage, along with PD-L1. Furthermore, alisertib treatment resulted in STING pathway activation, as indicated by increased phospho-STING_S366 and phospho-TBK1_S172 protein levels, in both human and murine SCLC cells. Conclusions: Our results demonstrate the potential of alisertib, the selective AURKA inhibitor, in modulation of PD-L1 and STING pathway activation in SCLC cells, thus supporting the rationale for in vivo testing with immunotherapy drugs. In particular, evaluation of this strategy in MYC-positive SCLC models could open new therapeutic investigations in this highly resistant SCLC subgroup. Citation Format: Carminia M. Della Corte, Liz Lauren Ajpacaja, Robert J Cardnell, Carl M Gay, Lixia Diao, Qi Wang, Kavya Ramkumar, Allison C. Stewart, Rebecca B. Kow, Hannah E Stumpf, You-Hong Fan, Jing Wang, John V Heymach, Lauren A. Byers. The Aurora kinase A-inhibitor, alisertib, is a potential candidate for combination with immunotherapy in small cell lung cancer [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr B064. doi:10.1158/1535-7163.TARG-19-B064